29 April 2014

A lot of ink and pixels have been spilled about the
FCC's new rules for
network
neutrality. It's impossible to comment sensibly yet about the actual
proposal, since as far as I know it's not been published anywhere, but
the various news reports have left me confused about just what is being
addressed. There are a number of different sorts of behavior that can
result in performance differences to the end user; it isn't always clear
which are covered by the phrase "network neutrality". Furthermore,
some of these items involve direct, out of pocket expenses for a
improvments in connectivity; this cost has to come out of
someone's wallet. The purpose of this post is to give a simplified
(with luck, not too horribly oversimplified) explanation of the different
issues here.

Note carefully that in this discussion, I am not trying to imply that
network neutrality is good or bad. I simply don't know of a less loaded
term.

Before I start, I need to define a few terms. Roughly speaking, there
are three types of users of the Internet:
content, eyeballs, and content
distribution networks.
"Content" is what we read, watch, or listen to:
news sites, movies, audio, etc. "Eyeballs" are consumers, the people who
read, watch, or listen to content. (Yes, eyeballs can listen to MP3s.
I never said that this post was anatomically correct.) Content distribution
networks (CDNs) are a special form of content: to avoid chokepoints when
sending out many copies of large files, such as images and movies,
content providers send out single copies to CDNs and let the CDNs
redistribute them. A CDN is just a set of data centers inside multiple
networks.

Some networks, such as most cable ISPs, are mostly eyeballs. (Again,
I'm oversimplifying; some cable ISPs do provide other services.)
There are
others that run hosting data centers; these are mostly content. Consumers
wouldn't sign up for Internet service if there was no content to watch;
content providers wouldn't be online if there were no consumers to
profit from. This raises the first interesting question: who
benefits more? That is, who should pay what percentage of the cost
for an interconnection between a content network and an eyeball network?

The really big ISPs (sometimes known
as "Tier 1" ISPs, though that phrase has become overly beloved by
marketers), like AT&T and Verizon, have both content and
eyeballs. When they interconnect, it's called peering: they're
equals, peers, so they split the cost of the interconnection.
Well, we think they split the cost; peering contracts are bilateral
and confidential, so no one outside really knows. (For those of you
who expect—or fear—discussion of BGP, autonomous systems,
and the default-free zone, you can relax; that's a level of detail
that's not really relevant here, so I won't be going into those issues.)

The situation is different for smaller players. They're not the equal
of the Tier 1s, so they have to buy transit. That is, for a
customer of a small ISP to reach a customer of a Tier 1, the ISP
has to pay some Tier 1 for transit services to the rest of the Internet.
(Yes, I said was simplifying things; I know it's more complicated.)

So what does all this have to do with network neutrality? Let's look
at several cases. The simplest is intranetwork, where the eyeballs and
two or more content providers are directly connected to the same ISP.
Will the consumer get the same experience when viewing both content
providers? If not, that's generally considered to be a violation of
network neutrality. That is, if the ISP is making decisions on
how much of its bandwidth the two content providers can use, there's
a violation.

Note that I've assumed that all parties pay enough for their own bandwidth
needs. An HD video stream takes about 6 Mbps; if I'm a content provider
trying to send different video streams to 100 customers simultaneously,
I'd better
have (and pay for) at least 600 Mbps of bandwidth to the ISP. If I
don't, my customers will get lousy service, but that's not
discrimination, it's physics.
Sometimes, though, it's hard to provide enough bandwidth. Wireless
ISPs (who have sometimes claimed that network neutrality rules would
be a hardship for them)
are limited by spectrum; their internal networks may have
ample capacity, but there's only a certain amount they can push out
to people's phones. This isn't discrimination, either—unless the
ISP makes a choice about which content to favor.

Life gets more complicated when traffic is entering the eyeball network
from outside. Eyeball networks are generally not Tier 1s; they buy transit.
If there's more demand for bandwidth than their current links can handle,
they have three choices: they can increase their bandwidth to their
transit providers, i.e., they can pay more for transit to connect their
eyeballs to the content they want, they can selectively favor certain
external content providers (which will give good service to some and
poor service to others), or they can let everyone suffer equally.
This last strategy leads to unhappy customers; the first strategy,
though, implies higher costs that someone will have to pay.
And the middle choice? That's where
network neutrality comes into play: who makes the decision?

Some content providers are willing to connect directly to eyeball ISPs.
Must the
eyeball ISP accept connection requests from all content sources? Who
pays for the interconnection? Note that at a minimum, the eyeball
ISP will need a dedicated router port, and someone has to pay for this port
the physical link to connect it to the content source.

The other choice, for a content source facing congested links, is to
deal with a CDN. This begs the question, though: CDNs need a presence
(or more than one) on every eyeball ISP. Who pays for this presence?
Does the eyeball ISP offer different terms to different CDNs, or turn some
down?

If you're still with me, you can see that "network neutrality" can
cover many different sorts of behavior.

Intra-network behavior, especially by wireless ISPs

Transit links purchased by eyeball ISPs

Direct connections between eyeball and content ISPs

Connections by CDNs

and probably more.
Which of these, if any, should be dealt with by regulation? Who should
pay for added links or increased bandwidth?

These are not idle questions. In one case that's been drawing a great
deal of attention,
Netflix has
blamed
"ISP trolls" like
Comcast for discriminatory policies.
Others, though, have claimed that Netflix
deliberately
used
an ISP (Cogent)
with a congested link to Comcast because it was cheaper for them.
Did Netflix make this choice? If so, why wasn't the
link between Comast and the ISP upgraded? Was one party refusing to pay
its proportionate share? (This is the sort of fact question that
can't be answered in the abstract, and I'm not trying to say who's right
or even what the facts are.)

If eyeballs are to get the content they want, some interconnection
facilities will have to be upgraded, either by new links or by
higher-speed links; this in turn means that someone
will have to pay for the upgrades, possibly beyond the
routine continual upgrades that all players on the Internet
have to do.
The network neutrality debate
is about who makes the decision and under what criteria. Furthermore,
the answers may be different for each of the cases I've outlined above.
When the FCC's rules come out, pay attention to all of these points
and not just the buzzwords: it isn't nearly as simple as "fast lanes for
big companies" versus "government meddling in the free market".